https://escholarship.org/content/qt8rf718jm/qt8rf718jm.pdf?t=krnesf

Recent Advances in Mechanical Micromachining

This paper presents an experimental investigation of micromachinability during micromilling of oxygen-free high conductivity (OFHC), commercially pure copper 101 using tungsten carbide micro-endmills. The forces, surface roughness, tool wear, and burr formation are analyzed under varying cutting speeds ( 40 , 80 , and 120 m/min) and feed rates ( 0.75 , 1.5 , 3 and 6 μ m / flute ). The experiments included full-immersion cutting with 254 μ m micro-endmills with an axial depth of cut of 30 μ m . The variation of forces, surface roughness, and burr formation with wear progression is also studied. It was seen that the minimum chip thickness and associated ploughing/indentation effects induce erratic variations to micromilling forces at feed rates in the vicinity of edge radius of the micro-endmills. At larger feed rates, the micromilling forces resemble those of conventional milling in the presence of tool-tip runout. The surface roughness was observed to be nearly constant at feed rates up to 3 μ m / flute , and to increase with feed rate for larger feed rates. Unlike conventional milling, greatest tool wear was experienced at the lowest feed rate and lowest speed, and the lowest wear was seen at the highest feed rate. The main mechanism of wear was concluded to be attrition wear in its most basic form, whereby the tungsten–carbide grains on the cutting edges were dislodged from the cobalt matrix. The smallest top burrs were experienced at 40 m/min surface speed at higher feed rates. The lowest feed rate of 0.75 μ m / flute resulted in large burrs at any speed. Progressing wear was seen to induce an increase in forces, a reduction in surface roughness, and a strong increase in burr formation.

An experimental investigation of micro-machinability of copper 101 using tungsten carbide micro-endmills

Multi-objective optimization using Taguchi based grey relational analysis for micro-milling of Al 7075 material with ball nose end mill

This review presents a systematic perspective on the development of micro-optofluidic lenses. The progress on the development of micro-optofluidic lenses are illustrated by example from recent literature. The advantage of micro-optofluidic lenses over solid lens systems is their tunability without the use of large actuators such as servo motors. Depending on the relative orientation of light path and the substrate surface, micro-optofluidic lenses can be categorized as in-plane or out-of-plane lenses. However, this review will focus on the tunability of the lenses and categorizes them according to the concept of tunability. Micro-optofluidic lenses can be either tuned by the liquid in use or by the shape of the lens. Micro-optofluidic lenses with tunable shape are categorized according to the actuation schemes. Typical parameters of micro-optofluidic lenses reported recently are compared and discussed. Finally, perspectives are given for future works in this field.

/pdf/micro-optofluidic-lenses-a-review-401erlm84k.pdf

Micro-optofluidic Lenses: A review

Mechanical microengineering is an easy and cheap way to fabricate microstructures; for example, molds for injection molding or hot embossing. Restrictions remain in the selection of materials and in the minimum structure size. Especially for cutting microstructures in steel, these limitations included the lack of available small tools and the poor surface quality. We discovered that microstructures can be cut in both brass and stainless steel workpieces by using ground hard metal micro end mills. The minimum groove width achieved is less than 50 μm for cutting brass and about 100 μm for cutting stainless steel. Burrs are removed by a subsequent diamond-cutting step or electrochemical polishing, respectively. Our results represent the first step toward a microstructured, resistant, and cheap mold made of steel, which is then used for mass production of plastic microstructures.

Microstructure grooves with a width of less than 50 μm cut with ground hard metal micro end mills

A novel polymer-based fluid-actuated variable focal length microlens system with a wide field-of-view (FOV) and large numerical aperture is designed and fabricated using standard photolithographic and silicon micromachining techniques. A flexible polydimethylsiloxane (PDMS) membrane is used to form the lens surface and is actuated by fluidic pressure applied by an external syringe pump. This lens system is capable of working in dual mode, forming either a double convex (DCX) or a double concave (DCV) lens. The relationship between the focal length (f) and FOV of the fabricated dynamic lens system as a function of the volume of the fluid pumped into or out of the lens chamber is investigated. The focal length of the dynamic lens system demonstrated in this paper could be tuned in the range of 75.9 to 3.1 mm and −75.9 to −3.3 mm for the DCX and DCV lens configurations, respectively. The FOV for this lens system was found to be in the range of 0.12 to 61° for DCX lens and 7 to 69° for DCV lens. The smallest F-number (f/#) that could be achieved using this dynamic lens is 0.61, which corresponds to the numerical aperture value of 0.64.

https://iopscience.iop.org/article/10.1088/0960-1317/14/12/010/pdf

Polymer-based variable focal length microlens system

Micromilling development and applications for microfabrication

Micromechanical milling has been shown to be a rapid and direct method for fabricating masks for deep x-ray lithography with lateral absorber features down to 10 micrometers. Conventional x-ray mask fabrication requires complex processes and equipment, and a faster and simpler method using micromechanical milling was investigated for larger microstructures for mesoscale applications. Micromilled x-ray masks consisting of a layered architecture of gold and titanium films on graphite yielded exposures in PMMA with accuracy and repeatability suitable for prototype purposes. A method for compensating milling tool radial runout was adapted, and the average accuracy of mask absorber features was 0.65 micrometers, with an average standard deviation of 0.55 micrometers. The milling process leaves some absorber burrs, and the absorber wall is tapered, which introduces an additional process bias. Mask fabrication by micromilling is fast and, therefore, less costly than conventional mask fabrication processes.

P. Coane

Papers

Polymer-based variable focal length microlens system

Micromilling development and applications for microfabrication

Direct fabrication of deep x-ray lithography masks by micromechanical milling

Electroless copper deposition on silicon with titanium seed layer

Design and fabrication of fluid controlled dynamic optical lens system